When using supporting implants it is important that the implant material has a high strength and that a sufficiently high resistance to shearing forces is developed between the implant and new grown bone tissue. The latter feature is important for achieving good retention. High strength implant materials can be achieved by using dense materials having an inherent high strength, such as conventional construction materials, for example stainless steel, cobalt-chromium alloys, titanium and titanium alloys, ceramic materials or polymers or materials with controlled defects, including pores.
For the fixation of implants to bone, it is known in the art to utilize a topographic surface or pores. Retention is achieved through the establishment of a good contact between the implant and new grown bone tissue.
Swedish Patent No. 468 502 discloses certain aspects relating to the pore size distribution in porous implant materials. Specific and complex pore size distributions in this respect have been found possible to use for depositing bone growth promoting substances and in order to stimulate a good bone ingrowth in larger pores.
Swedish patent application No. 9200072-8 describes how the microporosity of an implant can be utilized for the deposition of one or more bone growth promoting substances by means of carriers prior to implantation. By filling the pores to a different degree with carriers having a poor solubility, and with appropriate active agents, the formation of pores for bone ingrowth and for release of active substances can be controlled in order to achieve an optimal ingrowth.